1. Field of the Invention
The present invention relates to a method and apparatus for evacuating nitrous oxide exhaled by a patient, and more specifically, to an apparatus that can be positioned on a patient to evacuate exhaled nitrous oxide.
2. Related Art
Nitrous oxide is an anesthetic gas widely used in dental offices. It is typically administered with oxygen and functions primarily as a sedative to reduce anxiety during dental procedures. The exposure limit for nitrous oxide recommended by the National Institute for Occupational Safety and Health (NIOSH) is 25 ppm for an average exposure time of 8 hours. Levels of nitrous oxide found in dental offices may be substantially higher, typically ranging from about 100 ppm in offices that use anesthetic gas scavenging equipment to over 1000 ppm in offices that do not use such equipment.
Increased general heath problems and reproductive difficulties associated with exposure of non-patients to occupational levels of nitrous oxide have been described in scientific, medical and dental literature. Exposure to high levels of nitrous oxide typically found in dental offices has been found to adversely affect fertility in women (Roland A S et al., N Engl J Med, 1992, 327:993-997). Long-term exposure of male dentists to nitrous oxide in the dental operatory has been correlated with an increased incidence in liver and renal disease, spontaneous abortion in their wives, and general and non-specific neurologic disease. Among female chairside assistants, the association between long-term occupational exposure to nitrous oxide and these same general health and reproductive problems is more pronounced (Cohen E N et al., JADA, 1980, 101:21-31). It was found that dental professionals and assistants who worked with nitrous oxide exhibited a three- to four-fold increase in the incidence of neurological complaints, for example, numbness, tingling and/or muscle weakness, compared to non-anesthetic exposed dental employees (Brodsky J B et al., Anesthesia and Analgesia, 1981, 60:297-301).
A particular problem in the dental office environment is that the patient's mouth is open and nitrous oxide is released through the patient's mouth during respiration and conversation. This leads to the undesirable exposure of dental office personnel to excess levels of nitrous oxide.
In the past, it has been known to evacuate exhaled or trace concentrations of nitrous oxide by a combination delivery and evacuation system. One such system, sold by Porter Instrument Company, Inc., Hatfield, Pa., and known as the Porter/brown Scavenger (breathing circuit) System, provides a first outer mask for the delivery of nitrous oxide and a second inner mask nested within the outer mask for evacuation of exhaled nitrous oxide. The masks are designed to fit around the nose of a patient. However, these mask-based evacuation systems are limited to the evacuation of anesthetic gases that are exhaled by the nose, and do not evacuate gases that are exhaled from the mouth, or gases that otherwise leak from the system.
Accordingly, what is needed, but has not heretofore been provided, is an effective method and apparatus for evacuating nitrous oxide exhaled or released from a patient's mouth, or otherwise leaks from the nitrous oxide delivery or evacuation system, in a dental operatory which does not interfere with the performance of the dental procedure.